This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 165 |
| 4 | 4785 |
| 5 | 397155 |
| 6 | 97302975 |
| 7 | 71128474725 |
| 8 | 155700231173025 |
| 9 | 1021860617188563075 |
| 10 | 20115326249356864131375 |
| 11 | 1187830130350772183821825125 |
| 12 | 210422919761508941591852499068625 |
| 13 | 111827787746815596446398867662527275875 |